The present invention relates to a process for purifying d-Limonene, and in particular to a process for treating d-Limonene to remove odorous impurities therein.
d-Limonene is a naturally occurring, cyclic, olefinic, oil material found in citrus peels, having the basic formula C.sub.10 H.sub.16. d-Limonene is produced as a byproduct of processes used to make citrus products, such as frozen concentrated orange juice.
In a typical citrus processing plant, the citrus peels are squeezed to remove as much moisture as possible before being sent to a dryer where the peels are dried to produce an animal feed. The liquid squeezed from the peels is known as press liquor. Most typically, the press liquor is treated by a distillation process. The vapor phase from this process includes water and the d-Limonene, which are condensed and separated. The remainder is referred to as molasses. Sometimes d-Limonene is referred to as stripper oil because it is produced by stripping the press liquor.
d-Limonene has a number of uses. Traditionally, d-Limonene was mixed with fuel oils and used as a boiler fuel. In this regard, see U.S. Pat. Nos. 4,818,250 and 4,915,707 to Whitworth which disclose processes for purifying d-Limonene to avoid the formation of gums so that it can be blended with conventional petroleum fuels for motor, diesel and aviation fuel.
Another use for d-Limonene is to make glue. d-Limonene is also used in the production of aromatic compounds. U.S. Pat. No. 4,533,487 to Jones discloses a process for blending d-Limonene to produce a multi-use cleansing agent. Recently, d-Limonene has found utility as a replacement for fluorocarbons in cleaning solid state electronic parts.
Many of these uses of d-Limonene require a high purity product, and such high-purity products command a premium price. d-Limonene produced at citrus processing plants, however, quite commonly has odorous impurities which prevent it from being sold at the premium price. It is believed that these impurities result because of high temperatures used in the distillation operation, and possibly because the molasses has begun to burn on to the insides of the tubes through which the press liquor is fed during the distillation operation. One solution to the problem might therefore be to lower the distillation temperature. This, however, reduces the throughput capacity of the equipment, and additional equipment involves a large capital expenditure.
During the development of the present invention another problem was encountered. Sometimes d-Limonene treated to remove these odorous impurities ended up with off-color problems, which also prevented it from being sold at the highest possible price. Hence, there is a need for a process for treating d-Limonene to remove odorous impurities that preferably will not result in off-color d-Limonene.